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Discuss RTL-SDR and cheap software defined radio
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PostPosted: Tue May 16, 2017 3:14 pm 
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Joined: Sat May 13, 2017 4:02 pm
Posts: 14
The HAM bands seem to be very quiet in France...
I've hust received my RTLSDR Blog V3. It seems to work a lot better than the noname dongles. I haven't tried it with my discone because I need to buy a SMA to F type adapter. Is it better to use a straight adapter or a pigtail ? What is the easiest way to put a Male SMA on the Coax cable to go directly into the dongle ?

If I mount the antenna on the roof, do I need an 'ugly balloon' ? how many turns, what diameter ?

If I want to use the dongle under 20 Mhz, do I just need to use a long wire (how long ?) as an antenna ? What sort of wire ?

I've just noticed that on the rtl-sdr.com homepage, there's an article about the cantenna I was talking about for ADSB in my previous message. What a coincidence ;-)

Thanks again for all your help.

Regards,

James


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PostPosted: Thu May 18, 2017 7:43 am 
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Joined: Fri Apr 08, 2016 8:43 pm
Posts: 35
Hi James,

Activity on HF (2-30mhz) is dependent on radio propagation which can vary greatly by time of day/night, season and solar activity. It's a complex subject, there's a good write-up on wikipedia. There also isn't as much activity in general as there was years ago. Many short-wave broadcasters have shut down in favor of Internet streams and a lot of what you hear will be digital.

There's a gentleman in your country that posts listening reports of various pirate radio stations from around Europe. It would seem there's a lot of activity between 6 and 7 Mhz. I don't get much of that in the US but you might have some fun listening in on the anarchy! :) Here's the link, it's legit despite the URL.

http://www.easyshopdiscountzone.com/rad ... e/english/


These discones don't work as well on the short-wave bands. A dipole or long wire antenna will yield better results. You could get started with say, 40 feet (or more) of wire in your attic or even better out to a tree in your yard if you have such an arrangement. Solid or stranded, insulated or not, thickness isn't too important. There's also some good info on wikipedia about those antennas ... good info, not overwhelmingly complex. When you're ready to dive into the more technical aspects, amateur radio publications are all over the Interwebz.

As for adapters, straight adapters are physically more robust so preferable if used on the antenna end. Electrically/performance wise there's no difference.


-K


https://ranous.wordpress.com


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PostPosted: Thu May 18, 2017 8:13 am 
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Joined: Tue Dec 27, 2016 11:00 pm
Posts: 54
Discone antenna work very well on short wave!

however I wonder if you could fit it into your attic, since it will have to have much larger dimensions than yours to work on short wave :twisted: . Over at QRZ forums you will get some idea from this thread http://forums.qrz.com/index.php?threads ... hf.349996/

Image

PS.: The more efficient and wideband your antenna is, the more energy it will receive. In consequence it will overload most cheap receiver inputs. The only solution add a variable/switchable attenuater and/or and a tuneable Preselector or a number of bandpassfilters to reduce the energy that the receiver frontend is subjected to.

If you use magnetic antennas, you don't need any additional filter, but you have to retune the antenna since it is a resonant circuit whith limited bandwith, which is why you won't overload the receiver frontedn.

Have fun receiving


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PostPosted: Tue May 23, 2017 9:43 am 
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Joined: Sat May 13, 2017 4:02 pm
Posts: 14
Hello again,

Thanks to all of you for your help. I've just ordered a LNA4ALL with bias-t and a few F type to sma adaptors. We will see how it goes.
If I still don't receive much, I'll put the antenna on the roof.

Regards,
James.


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PostPosted: Tue Jul 11, 2017 12:27 am 
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Joined: Mon Jul 10, 2017 11:31 pm
Posts: 7
James_from_France wrote:
The HAM bands seem to be very quiet in France...




James, I'm a n00b when it comes to SDR, but a long time ham. I know there's a lot of ham activity in Europe because I can here it here from the states.

For HF activity (say, 7Mhz-7.2Mhz) just unspool 30' of wire out the window, or taped to the top of a wall, or in the bushes, etc. At night in particular, you should have a ton of signals in your waterfall. Inside or outside the roof, there will be no practical difference at HF.

Keep in mind they will be in CW or Lower Sideband (LSB).

Let us know how it rolls...

John


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